I guess it might be partly out of morbid curiosity, but I have wondered for some time now, how do children of incest usually turn out? Are they hideously deformed usually? When I was smaller people used to say children of incest were typically retarded. Is that true?

I'm talking about people very closely related having children together. Redneck jokes notwithstanding, I am not talking about cousins here either. Queen Victoria married her first cousin Albert. And all of their children came out alright.

So what is the usual outcome of very close relations?

Thank you in advance to all who reply

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If the two parents didn't have "hideously deformed" genes, why would the kids? The only unusual occurrence would be if both parents have the same recessive gene (which may be a "positive" trait or "negative", which is more likely the closer they are related. If there are no undesirable genes to begin with, no problem.

Except that all humans have some number of rare recessive genes that almost never manifest without incest, since they're so rare. And when one gene is significantly better or worse than another, it's almost always the recessive that's the bad one, because defective dominant genes get selected out of the gene pool very quickly.

In many, but not all (see Incest taboo) cases, incest is also inbreeding. Although jurist Henry Maine first argued that incest necessarily leads to an increase in congenital birth defects, this is not necessarily the case. Inbreeding does not directly lead to congenital birth defects per se, it leads to an increase in the frequency of homozygotes.[34] An increase in homozygotes has diverging effects. A homozygote encoding a congenital birth defect will produce children with birth defects, but homozygotes that do not encode for congenital birth defects will decrease the number of carriers in a population. The overall consequences of these diverging effects depends in part on the size of the population. In small populations, as long as children born with heritable birth defects die before they reproduce, the ultimate effect of inbreeding will be to decrease the frequency of defective genes in the population; over time the gene pool will be healthier. In larger populations, however, it is more likely that large numbers of carriers will survive and mate, leading to more constant rates of birth defects.[35]

So inbreeding is actually kind of beneficial for the gene pool, just as long as your kids don't get in on the act too.

I'm talking about people very closely related having children together. Redneck jokes notwithstanding, I am not talking about cousins here either. Queen Victoria married her first cousin Albert. And all of their children came out alright.

Inbreeding and linebreeding is a great way to set desirable inheritable traits. It's also a dandy method to set undesirable traits. In nonhuman animals, this can be a good thing. You breed the various animals that are healthy, and you cull, or at least don't breed, the ones that have the undesirable traits. With humans, well, most people are uncomfortable with the notion that people with undesirable traits shouldn't be allowed to breed.

For further reading, I suggest Googling the words hemophiliac royal or inbreeding linebreeding and the phrase "popular sire syndrome".

Brother and sister, separated at birth, meet, fall in love, have children, find out they are siblings. Not only in the movies. In Spain. Adult children are normal and have no psycological problems or otherwise. The family is not ashamed or shy about the case.http://www.elmundo.es/cronica/2005/495/1113084017.html

A simple way to understand it is by analogy with cards: Every family has a deck of cards, representing their gene pool, and there are complex rules determining what comes out of any particular hand. A good rule to remember is that mostly pairs or other combinations actually have an observable outcome (expression in the phenotype).

Every child gets a hand created out of shuffling their parents' cards. Outbreeding, the usual way to select mates in our culture, ensures that the number of pairs is kept fairly low: Mom's hand isn't especially similar to dad's hand, so junior won't end up with a lot of repeats. Additionally, cards combinations that result in hands that never get reshuffled (people who never breed) will be destroyed and their component cards will be so lost in the shuffle they're essentially nonexistent. (This is why so few babies are born without lungs, for example.)

Inbreeding, however, keeps all the same cards circulating from one generation to the next. This results in pairs, flushes, and even inside straights, or, in genetic terms, a larger amount of phenotypes that are rare in the general population.

This doesn't always mean diseases. However, it results in diseases often enough that inbreeding is mostly a bad idea. Mainly, this is because we don't (and, to some extent, can't) do detailed genetic testing of our prospective mates. Hemophilia in European royalty is a famous example of what can result from a particularly intensive long-term human inbreeding project. One of the most dramatic examples was Charles II of Spain, also known as Charles the Hexed, who was descended from Joanna the Mad 14 different ways.

I knew a woman a few years ago whose son had married her younger sister(his maternal aunt). They had three children, who were apparently slow but not deformed. The worst part was the taboo - it really broke her heart that her sister and son could do such a thing.

Hemophilia in European royalty is a famous example of what can result from a particularly intensive long-term human inbreeding project. One of the most dramatic examples was Charles II of Spain, also known as Charles the Hexed, who was descended from Joanna the Mad 14 different ways.

See The Master on pedigree collapse. Charles II had a terrible case of pedigree collapse.

Norway's current king, Harald V, is the son of a first cousin marriage. His father was also the son of a first cousin marriage. Okay, he has a big nose and a rather pronounced case of male pattern baldness, but I don't think you can call him deformed. He's also somewhere around average on the intelligence scale.

Intermarriage among the royal families of Europe was the normal thing up until the early 20th century. You can certainly find examples of children born with serious problems because of that, and even today certain traits (like dyslexia) seem to be more widespread among the royals than the general population, likely because of the pedigree collapse issues. But most of the babies of these first cousin marriages were born quite normal. Cousin marriages make it more likely that the bad stuff hidden in the genes will come out in the babies - but they do not create new mutations.

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Take Queen Cleopatra (VII), who had love affairs with two of the most powerful men in the world, Julius Caesar and Mark Antony.

Her parents were uncle and niece, and were also first cousins. Her paternal grandparents were brother and sister. Her maternal grandparents were uncle and niece. Five (or six, depending on which way you ascend) generations up, she only had two ancestors, Ptolemy VIII and Cleopatra III -- and those two were uncle and niece. http://en.wikipedia.org/wiki/Ptolemaic_dynasty. All that inbreeding didn't seem to hurt her.

As far as I can tell in my near-total uneducation on the subject, most families can handle one incident of inbreeding. But if it continues, decline sets in fairly quickly. A couple of years ago I was reading about the Egyptian pharaohs, who were in the habit of marrying their own siblings. You could kind of see it in the mummies illustrated--the first generation would look OK, the second not so much, the third would be pretty strange-looking, and then they would have to find someone else to be Pharaoh, because by that time it was hard to produce a living child from the union. Each successive generation would have more miscarriages and fewer live births.

Everyone carries a few spontaneous deleterious recessive mutations. These only manifest if two people carrying the same mutation have children, and even then they only show up in 1/4 of all children. In the general population, out-breeding means that any two individuals won't carry the same mutations the vast majority of the time.

Let's start with a non-related pair. Each parent will have a handful of these recessive alleles - let's go with four each* (eight total), to make the math simpler. In their children, each will inherit (on average) half of these parental mutations, so they'll carry four. Any two of their children, again on average, will be carrying two of the same mutations. If these siblings reproduce, then the next generation (grandchildren of the original non-related pair) will have a 1/4 chance of expressing either individual mutation, which works out to be a 3/16 chance of expressing at least one. Also, they'll have a 12/16 chance of not expressing anything, but still being carriers.

This is a vastly higher risk of genetic disease compared to the general population, but it's hardly a guarantee. A lot of these mutations will also lead to infertility for the inbreeding couple, or very minor problems for their children. Hemophilia isn't easy to deal with, but it's not a death sentence either. So the products of incest won't be hideously deformed monsters, but they'll have a much higher risk of genetic disease. However, if you keep inbreeding for generations, the genetic problems will accumulate and become fixed, so that they become very prevalent. This is what happened with the European royal family, and similar things have been documented in other cases.

*perhaps too small, even. I've heard estimates of around 5-10 new deleterious recessives in every individual, but I can't find a cite at the moment... it's something that's been mentioned repeatedly in many of my classes and textbooks on genetics.

My mom used to work as a social worker and she said that there was a higher incidence of kids with physical and mental handicaps in the areas that she worked in than in other areas in the Netherlands. This, she argued persuasively, was due to the social structure in those areas (fishing villages), where there's a lot of different churches. The people there don't want to marry outside the church but their communities are very small so they're faced with generations and generations of first-cousin marriages and the like. While it is not possible to tell whether individual instances of handicaps and disease are caused by this, it's apparently pretty clear that on the aggregate level, there's a strong difference between these villages and other parts of the Netherlands.

I don't have any knowledge about children who are the product of incest, but this article is an interesting discussion on the pros and cons of inbreeding.

It's all about how you phrase it: "The chances of defects increases 2%." or "The chances of defects doubles." Most people see the first as no big deal and the second as a major concern despite being the same thing. I.e. people are bad at understanding statistics.

And that's just the "one off" case. Letting large numbers do it with no controls would get ugly.

In the thread about possible revolutionary technologies, I considered (but didn't post there) the idea that gene therapy might make it possible for siblings to guarantee that they wouldn't pass on any defective genes to their children. In fact, if you're going to go the full "Gattaca" route and laboriously engineer people, breeding "within the blood line" might actually be preferable.

The royal families had interbred for generations before hemophilia showed up.

I would like to point out that inbreeding did not cause the hemophilia that ran rampant through European royalty. Inbreeding does not somehow 'damage' the genes; it simply increases the chance of two deleterious mutations being paired together. With regard to hemophilia, the gene was so dangerous because a carrier mother has a 50/50 shot of producing a hemophiliac son. Because Queen Victoria's numerous progeny intermarried with almost every other royal house, they spread the gene to their descendants. Tsar Nicholas II was not a hemophiliac nor a descendant of Victoria; his wife Alix, however, was a descendant of Victoria and a carrier for the gene.

I've heard of studies where mice will not mate with their first cousins in the wild, only 2nd cousins or more (sorry, no cite).

I also was under the impression that inbreeding within the same generation (i.e. brothers and sisters) was not as bad as back-crossing (child with a parent). These back-crosses are more likely to produce the mutant phenotypes.

I also was under the impression that inbreeding within the same generation (i.e. brothers and sisters) was not as bad as back-crossing (child with a parent). These back-crosses are more likely to produce the mutant phenotypes.

On average, a pair of siblings are as closely related as a parent-child pair, but siblings vary randomly in how closely they're actually related.

The basic problem is that all of us are carrying some random recessive mutations in our genetic code (for example, many people are carrying a gene that codes for Cystic Fibrosis but don't even know they have it, because Cystic Fibrosis is a recessive disease and only expressed if you inherit a copy of the defective gene from *both* parents, not just one) . Fortunately, when you mate with someone who isn't a close relative, the odds are that person doesn't have much genetic code in common with you and whatever defective recessive gene you have will be compensated for by the healthy gene for that trait the other person can contribute. Sometimes, of course, through random bad luck you do end up finding out your partner has the same disease-causing mutation (which is why unfortunately sometimes even unrelated couples have kids with diseases like Cystic Fibrosis)

With incest, the risk of a relative having the *same* recessive defect you do is higher than it would be in the general population. If incest occurs over more than one generation, it becomes an increasingly higher risk of having recessive genetic diseases show up that random mating with unrelated people never would have uncovered.

Look at purebred dogs. Most purebred dogs have had a lot of inbreeding in their family tree to make sure the desired traits of the breed were not lost. Purebred dogs aren't "hideously deformed" but many breeds do suffer from various genetic health problems because of the inbreeding. The same goes for "inbred" people - they won't be hideously deformed, won't necessarily be mentally retarded, but they will probably have more health problems in general than the average person.

Norway's current king, Harald V, is the son of a first cousin marriage. His father was also the son of a first cousin marriage. Okay, he has a big nose and a rather pronounced case of male pattern baldness, but I don't think you can call him deformed. He's also somewhere around average on the intelligence scale.

His son is HOT, though.

Charles II of Spain is an example of generations of inbreeding. Supposedly he had such a severe underbite he couldn't even chew his food, his tongue was so large he could hardly speak etc.

And Lynn, Anne Neville is correct-hemophillia had nothing to do with inbreeding. At least two of her daughters were carriers (Princess Louise never had any children so isn't known if she was one or not) so she would have been born with the gene. So it was either spontaneous, or she somehow inherited from her mother.

And Lynn, Anne Neville is correct-hemophillia had nothing to do with inbreeding. At least two of her daughters were carriers (Princess Louise never had any children so isn't known if she was one or not) so she would have been born with the gene. So it was either spontaneous, or she somehow inherited from her mother.

According to the geneticist Prof. Steve Jones, the hemophilia mutation almost certainly occurred in Victoria's father's sperm. There was no sign of the disease in the royal family before Victoria started to have children, and such mutations are commonly associated with elderly fathers (her father, the Duke of Kent, was in his fifties when Victoria was conceived).

You wouldn't have some cite for that, would you? I vaguely recall seeing some context for the image a while ago but I've forgotten all the details and I can't google it back up again now.

Unfortunately, I can't find the cite just now (could've sworn it was on Snopes), but what I remember is that they're Australian, their ancestry is as normal as yours or mine, and that they're locally renowned for their homeliness.

Unfortunately, I can't find the cite just now (could've sworn it was on Snopes), but what I remember is that they're Australian, their ancestry is as normal as yours or mine, and that they're locally renowned for their homeliness.

According to the geneticist Prof. Steve Jones, the hemophilia mutation almost certainly occurred in Victoria's father's sperm. There was no sign of the disease in the royal family before Victoria started to have children, and such mutations are commonly associated with elderly fathers (her father, the Duke of Kent, was in his fifties when Victoria was conceived).

That makes sense. (Although I read a theory that Victoria was actually a bastard as well. Hehehe!)

It's all about how you phrase it: "The chances of defects increases 2%." or "The chances of defects doubles." Most people see the first as no big deal and the second as a major concern despite being the same thing. I.e. people are bad at understanding statistics.

And that's just the "one off" case. Letting large numbers do it with no controls would get ugly.

That is not the same thing. If you have a certain defect that appears in 1 of 10,000 births naturally, then you have a 1/10,000 chance of each birth affected, or 0.0100%.

If the chances of that defect increase by 2%, then you have a 1.02/10,000 chance = 0.0102% chance. Another way to do the math is you take the original percentage and add 2%: 0.010% + .02*0.010%= 0.0102%

If you double the chances, then you have a 2/10,000 chance = 0.0200%. or, doubling the chances is the same as saying "increase by 200%".

This is not true. The "rat children of Gujrat" are microcephalics who are sold into a life of begging, or abandoned by families who are unable or unwilling to care for them. There is an argument that ordinary babies are purposefully deformed in order to make more money as beggars, but it's a contentious assertion, to say the least. Close relatives having children may have something to do with it, though (information in the last article).

From what I've seen this photo has mainly pooped up and been referenced as a pair of (IIRC) Appalachian (or similar hardscrabble region) brothers from the first half of the 20th century (Depression era I believe) . It would be interesting to know their real origin.

Those Appalachian / Australian (?) brothers aren't that bad. Putting on a mean, frowny expression will make most folks look hideous. I see equally ugly people on a weekly basis (the bro's do have world-class Dumbo ears, though).

I do not see anything unreal about that photo or even much outside the usual except for the ears sticking out which some people have (ask Camilla). The frown on their expressions and the hideous haircuts will do the rest. with a different haircut which covered their ears more they would not be noticeable at all.

That is not the same thing. If you have a certain defect that appears in 1 of 10,000 births naturally, then you have a 1/10,000 chance of each birth affected, or 0.0100%.

If the chances of that defect increase by 2%, then you have a 1.02/10,000 chance = 0.0102% chance. Another way to do the math is you take the original percentage and add 2%: 0.010% + .02*0.010%= 0.0102%

If you double the chances, then you have a 2/10,000 chance = 0.0200%. or, doubling the chances is the same as saying "increase by 200%".

Not the same thing.

I have absolutely no idea where you are pulling those numbers from. The original study cited says that birth defects went up from 2% to 4%. That's a doubling. Unfortunately, as the linked article focuses on, the media tended to state that the increase was an additional 2%.

My friend's family has two first cousins marry each other. They have 2 children. The son has extreme paranoia about aliens and government and people following him. The daughter has a cleft lip and is crazy too.